Hi 70sgirl,
I don’t know the specifics of your mattress but what you are describing could be coming from the softening or breakdown of materials in your mattress (particularly in the upper layers) or from changes in your body and your specific needs and preferences (which change with time and circumstances).
Your mattress may not be all latex and its quite possible that there is polyfoam in your mattress as well which could be breaking down (you can check the law tag to see the materials in your mattress). Softer latex also won’t last as long as firmer latex.
Either way … it appears that the mattress is no longer a good match for you in terms of PPP.
The membrane types of waterproof covers are not as breathable as other types of covers and they certainly sleep warmer for some people because of this. There is more about the different types of mattress protectors in post #89 here and more about all the factors that can affect sleeping temperature in post #2 here. It’s often a combination of several factors that leads to a mattress sleeping warmer.
Just in case you haven’t read it yet … the first place to start when you are looking for a new mattress is the tutorial post here which has all the basic information, steps, and guidelines you will need to make the best possible choices … and avoid the worst ones.
Phoenix